A chemically amplified positive resist composition is used for semiconductor microfabrication. As the chemically amplified positive resist composition, a chemically amplified positive resist composition comprising a resin which contains a structural unit having an acid-labile group and which itself is insoluble or poorly soluble in an alkali aqueous solution but becomes soluble in an alkali aqueous solution by the action of an acid and an acid generator comprising a compound which is not a polymer and which generates an acid by irradiation has been used (e.g. J. Photopolym. Sci. Technol., 11, 1998, 379).
In semiconductor microfabrication, it is desirable to form patterns having high resolution, and especially, in ArF excimer laser lithography process, extreme ultraviolet (EUV) lithography process and electron lithography process, it is desirable to give patterns having higher resolution, and it is expected for a chemically amplified resist composition to give such patterns. In liquid immersion lithography process, the cation and anion components derived from the acid generator usually elute in water or a solvent having a high refractive index and it is expected for suppressing the elution of the cation and anion components.